It looks like reason is game selector menu, it seems to have different screen position than normal WB disk. If booted from WB 1.3 disk, screen position is not overscanned and all sprites are available.

EDIT: This also explains OCS/ECS difference. With OCS sprite 6 is corrupted and 7 disabled. With ECS sprite 6 works and 7 stays disabled. Only if screen mode is not overscanned sprite 7 is visible (both OCS and ECS) and game works as expected.